Circuit Description
The knock sensor (KS) system is used to detect engine detonation, allowing the engine control module (ECM) to retard ignition control spark timing based on the KS signal being received. The KS produces an AC signal so that under a no knock condition the signal on the KS circuit measures about 0.007 volts AC. The KS signal's amplitude and frequency depend upon the amount of knock being experienced. The ECM contains a non-replaceable knock filter module called a signal-to-noise enhancement filter (SNEF) module. This filter module in the ECM determines whether knock is occurring by comparing the signal level on the KS circuit with the voltage level on the noise channel. The noise channel allows the ECM to reject any false knock signal by knowing the amount of normal engine mechanical noise present. Normal engine noise varies depending on engine speed and load. When the ECM determines that an abnormally low noise channel voltage level is being experienced, diagnostic trouble code (DTC) P0327 will set.
Conditions for Setting the DTC
| • | The knock sensor serial peripheral interface (SPI) bus in failure for 10 seconds. |
| • | The calculated airflow is higher than 180 mg/tdc |
| • | The knock sensor voltage is below 0.3 volts. |
| • | Engine coolant temperature is higher than 60°C (145°F). |
| • | The engine speed is greater than 1,500 RPM. |
| OR |
| • | When the difference between an original signal valve and filtering valve is less than 5 percent. |
| • | The engine coolant temperature is greater than 60°C (145°F). |
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate after 3 consecutive trips with a fail. |
| • | The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers. |
| • | A history DTC is stored. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after 4 consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | DTCs can be cleared by using the scan tool. |
| • | Disconnect the ECM battery feed for more than 10 seconds. |
Diagnostic Aids
| • | Inspect and correct any abnormal engine noise before using the diagnostic table. |
| • | Any circuitry that is suspected as causing an engine noise complaint should be thoroughly inspected for the following conditions : |
| - | Backed-out terminals |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed |
| - | Damaged terminals |
| - | Poor terminal-to-wire connections |
| - | Physical damage to the wiring harness |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Perform a Diagnostic System Check. Is the system check complete? | -- | Go to Step 2 | |
2 |
Does the malfunction indicator lamp (MIL) illuminate? | -- | Go to Step 4 | Go to Step 3 |
3 |
Does the malfunction indicator lamp (MIL) illuminate? | -- | Go to Step 4 | Go to Step 12 |
4 | Listen to the engine while raising and lowering the engine speed. Is a knock or audible noise present? | -- | Go to Step 5 | Go to Step 6 |
5 | Repair the mechanical engine problem, a loose bracket, or a component. Did you complete the repair? | -- | Go to Step 12 | -- |
6 |
Is the measured value within the specified range? | 90-110 k ohms | Go to Step 7 | Go to Step 9 |
7 | Inspect for a poor connection at the ECM connector and knock sensor (KS) signal circuit and repair as necessary. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 8 |
8 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | Go to Step 10 |
9 | Inspect the KS electrical connector for a poor connection and repair as necessary. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 |
10 | Inspect the KS signal circuit for an open or a low voltage, or voltage, and repair as necessary. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 |
11 | Replace the KS. Knock Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | Go to Step 13 | Go to Step 2 |
13 | Are any DTCs displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK |
